N_2O_4/O_3硝化芳烃反应的宏观动力学研究

Macro-kinetics Study of Ozone-mediated Nitration Reaction of Aromatic Compounds with Nitrogen Tetroxides

讨论了N2O4/O3硝化芳烃的动力学行为,利用稳态处理方法得出了反应动力学模型。Raman光谱显示N2O4/O3反应体系不存在硝酰阳离子,说明N2O4/O3硝化芳烃不是硝酰阳离子的亲电取代过程。N2O4/O3硝化苯和甲苯时,反应速率对苯和甲苯的浓度为零级、对四氧化二氮为0.5级;当N2O4/O3硝化氟苯时,反应速率对氟苯为1级、对四氧化二氮为零级,实验结果与动力学模型相吻合。通过竞争实验测定出N2O4/O3硝化芳烃的哈米特方程logfRP=-7.26σ+p-0.125,反应常数为-7.26,与混酸硝化取代芳烃的反应常数相近,说明这两种硝化反应过程中决定异构体分布的过渡态具有相似结构。

The kinetics character in ozone-mediated nitration aromatic compound reaction with nitrogen tetroxide has been studied. Kinetics model has been constructed with the aid of stable state treatment method. Raman spectrum shows no nitronium ion in N_2O_4/O_3, which demonstrates N_2O_4/O_3 nitration aromatics is not a affinitive electronic substitution process. Experiment results show that the reaction rate of N_2O_4/O_3 nitration benzene and toluene is zero order in benzene and toluene, half order in N_2O_4, the reaction rate of N_2O_4/O_3 nitration fluorobenzene is first order in fluorobenzene, zero order in N_2O_4. By competing reaction, Hamett's equation of N_2O_4-O_3 nitrating substituted aromatics is obtained with logf^R_H=-7.26σ^+_p-0.125. The reaction constant (ρ=-7.26) is approaching to the result of mixture acid nitrating substituted aromatics, which shows the transition state that decides isomer distribution during two kinds of nitrating reaction has similar structure.